Hydrogen peroxide is an important intermediate chemical useful in such applications as water treatment, pulp and paper bleaching, and organic synthesis. At present, the commercial process for producing hydrogen peroxide involves anthraquinone autooxidation (see, e.g., U.S. Pat. Nos. 4,428,923 and 6,524,547). The process requires numerous reaction and purification sections, uses a large volume of solvent, and provides a less-than-ideal yield of hydrogen peroxide.
Hydrogen peroxide can also be made by a direct reaction of hydrogen and oxygen in the presence of a suitable catalyst, particularly a noble metal catalyst (see, e.g., U.S. Pat. Nos. 4,335,092, 4,772,458, 5,236,692, 5,846,898, 5,961,948, 6,168,775, 6,284,213, 6,375,920, 6,387,346, 6,630,118, 6,649,140; U.S. Appl. Pub. Nos. 2003/0215383, 2004/0151658, and 2005/0025697). A promoter such as chloride, bromide, iodide (e.g., NaBr, HBr) can improve hydrogen peroxide yield. However, these promoters are generally soluble in the reaction solvent and their recovery is troublesome. EP 0 498 166 A1 discloses a hydrogen peroxide-producing method using a catalyst comprising a platinum group metal catalyst impregnated with an organic halogen-containing compound that is insoluble in water.
Despite these efforts, new processes for making hydrogen peroxide from hydrogen and oxygen with improved productivity and selectivity need to be developed.